Coronary artery disease remains the leading cause of morbidity and mortality in Western societies. Coronary artery disease is manifested in a number of ways. For example, disease of the coronary arteries can lead to insufficient blood flow to various areas of the heart. This can lead to the discomfort of angina and the risk of ischemia. In severe cases, acute blockage of coronary blood flow can result in irreversible damage to the myocardial tissue including myocardial infarction and the risk of death.
A number of approaches have been developed for treating coronary artery disease. In less severe cases, it is often sufficient to merely treat the symptoms, with pharmaceuticals, or treat the underlying causes of the disease, with lifestyle modification. In more severe cases, the coronary blockage can be treated endovascularly or percutaneously using techniques such as balloon angioplasty, atherectomy, laser ablation, stents, and the like.
In cases where these approaches have failed or are likely to fail, it is often necessary to perform a coronary artery bypass graft (CABG) procedure. CABG surgery, also known as “heart bypass” surgery, generally entails the use of a graft or conduit to bypass the coronary obstruction and, thereby provide blood flow to the downstream ischemic heart tissues. The major objective of any CABG procedure is to perform a technically perfect anastomosis of the graft with the vessel. Creation of a technically perfect anastomosis is generally complex, tedious, time consuming and its success is highly dependent on a surgeon's skill level.
The CABG procedure is typically conducted on an arrested heart while the patient is on a cardiopulmonary bypass (CPB) circuit, also known as a “heart-lung machine” that provides continuous systemic blood circulation, while cardioplegic cardiac arrest enables meticulous anastomosis suturing in a bloodless, still-heart, operating field. In a CPB procedure performed as an adjunct to a CABG procedure, the patient's venous blood that normally returns to the right atrium is diverted to a CPB system or circuit that supplies oxygen to the blood and removes carbon dioxide from the blood and returns the blood, at sufficient pressure, into the patient's aorta for further distribution through the arterial system to the body. Creation of the CPB circuit typically entails arterial and venous cannulation, connecting the bloodstream to a heart-lung machine, cooling the body to about 32° Celsius, cross clamping of the aorta, and cardioplegic perfusion of the coronary arteries to arrest and cool the heart to about 4° Celsius. The arrest or stoppage of the heart is generally required because the constant pumping motion of the beating heart would make surgery upon the heart difficult in some locations and extremely difficult if not impossible in other locations. Generally, such a CPB system requires several separate components, including an oxygenator, several pumps, a reservoir, a blood temperature control system, filters, and flow, pressure and temperature sensors.
A blood vessel or vessels for use in the graft procedure are harvested or mobilized from the patient. In the majority of patients, obstructed coronary arteries are bypassed using an in situ internal mammary artery (IMA) or a reversed segment of saphenous vein harvested from a leg although other graft vessels may also be used. For this reason, CABG surgery is typically performed through a median sternotomy, which provides access to the heart and to all major coronary branches. A median sternotomy incision begins just below the sternal notch and extends slightly below the xiphoid process. A sternal retractor is used to spread the left and right rib cage apart for optimal exposure of the heart. Hemostasis of the sternal edges is typically obtained using electrocautery with a ball-tip electrode and a thin layer of bone wax. The pericardial sac is opened thereby achieving direct access to the heart. One or more grafts are attached to the relevant portion of a coronary artery (or arteries) to bridge the obstruction while the heart is in cardiac arrest. Then, the patient is weaned from CPB, the heart is restarted, and cannulation is discontinued. The surgical incisions in the chest are then closed.
The CABG procedure is generally expensive, lengthy, traumatic and subject to patient risk. The arrest of the heart and the use of the CPB circuit add to the time and expense of the CABG procedure and present a number of risk factors to the patient. The initiation of global (hypothermic) cardiac arrest may result in global myocardial ischemia, and cross clamping the ascending aorta may contribute to the patient experiencing a post-operative stroke. In fact, recent studies have shown aortic clamping and manipulation may release atherosclerotic debris into the bloodstream, resulting in neurological injury. Exposure of blood to foreign surfaces results in the activation of virtually all the humoral and cellular components of the inflammatory response, as well as some of the slower reacting specific immune responses. A systemic inflammatory response can result due to the interactions of blood elements with the artificial material surfaces of the components of the CPB circuit. Other complications associated with cardiopulmonary bypass include loss of red blood cells and platelets due to shear stress damage. In addition, cardiopulmonary bypass requires the use of an anticoagulant, such as heparin that increases the risk of hemorrhage. Cardiopulmonary bypass also sometimes necessitates giving additional blood to the patient that may expose the patient to blood-borne diseases, if it is from a source other than the patient. Therefore, a number of cardiac surgical procedures have been developed or proposed to enable off-pump, beating heart, CABG procedures either through a median sternotomy or employing minimally invasive procedures and even totally endoscopic procedures with access through ports extending through the chest wall into the thoracic cavity.
In one approach, pressure is applied against at least a portion of the heart to stabilize it and facilitate CABG or beating heart procedures as exemplified by the stabilization apparatus disclosed in U.S. Pat. Nos. 5,875,782, 6,120,436, and 6,331,158, for example. In one embodiment disclosed in the '436 patent, a U-shaped platform is pressed against the heart surface exposed through a thoracotomy and maintained there by suturing the platform to the myocardium or by attaching the platform to the end of an adjustable arm. The adjustable arm is mounted to a sternal retractor frame maintaining the ribs spread apart, and the adjustable arm can be adjusted to direct pressure through the platform against the heart to stabilize it. In addition, mechanical systems for lifting the heart, particularly to enable access to the heart for performing valve surgery, have been proposed as exemplified in the apparatus disclosed in U.S. Pat. No. 6,558,318.
In another approach, suction is applied to the epicardium of the heart to stabilize an area of the heart. Typically, an elongated shaft is coupled to a distal suction member, and a vacuum is drawn through a lumen of an elongated shaft or a vacuum line to apply suction to the epicardium to grasp and stabilize it. Suction-assisted tissue-engaging devices for cardiac surgery having circular or horseshoe-shaped suction members introduced through a sternotomy are disclosed in U.S. Pat. Nos. 5,727,569, 5,782,746, 6,071,295, and 6,602,183 and in U.S. Patent Application Publication 2002/0045888, for example. In certain cases, flexible suction tubes or vacuum lines extend from each suction member to an operating room vacuum source. The vacuum lines are bonded to elongated shafts of a forceps type device shown in certain forceps embodiments or the '569 patent. In other cases, a vacuum is drawn through one or more suction lumen within the rigid shaft of the suction application device coupled to the suction member.
Early versions of the Medtronic® Octopus™ tissue stabilizer used to apply suction to and thereby stabilize a site of the beating heart are disclosed in commonly assigned U.S. Pat. Nos. 6,464,630 and 6,394,948, for example. In certain embodiments, the tissue stabilizer employs a single elongated suction pod fixed at the distal end of an elongated shaft to extend substantially axially and distally to the elongated shaft distal end. It is necessary to employ two such elongated shafts and suction pods to place the suction pads on either side of the heart surface to be stabilized. In the schematically depicted embodiment of FIG. 33 of the '948 patent, the distal suction member comprises a horseshoe-shaped suction pod extending from the shaft distal end. In these embodiments, the shaft is malleable to shape it so as to apply the suction pod against the heart tissue at the site. A vacuum is drawn through a lumen of the shaft to apply suction at the suction ports of the suction pod.
Various current models of the Medtronic® Octopus tissue stabilizer and/or Medtronic® Starfish™ heart positioner and accessories, both available from the assignee of the present invention, have improved articulating arms supporting distal suction members. The Medtronic® Octopus 3™ tissue stabilizer is approved for use in applying suction to a surface of the heart to stabilize the heart tissue at the site of engagement while the heart is beating to facilitate a surgical procedure, e.g., to perform an anastomosis in the course of a CABG procedure. The Medtronic® Starfish™ heart positioner is approved for use in applying suction to a surface of the heart, particularly near the apex of the heart, to move and reposition the heart to achieve better access to areas that would otherwise be difficult to access, such as the posterior or backside of the heart. For example, the surgeon can bring an anastomosis site into better view by supporting and rotating the heart using the Starfish™ heart positioner. The surgeon can also use the Octopus 3™ tissue stabilizer in the same procedure to stabilize the anastomosis site. See, for example, commonly assigned U.S. Pat. Nos. 5,836,311, 5,927,284, 6,015,378, 6,464,629, and 6,471,644, and European Patent Publication No. EP 0 993 806 describing aspects of the Octopus 3™ heart stabilization system, commonly assigned U.S. Patent Application Publication U.S. 2002/0095067 disclosing aspects of the Starfish™ heart positioner, and commonly assigned U.S. Patent Application Publication U.S. 2002/013809 disclosing use of both in the same surgical procedure.
The Octopus 3™ tissue stabilizer and the Starfish™ heart positioner are both provided with an elongated articulating arm that extends between a proximal clamp and a distal suction member. These suction-assisted, tissue-engaging devices are used in open chest sternotomy procedures that involve making a 20 to 25 cm incision in the chest of the patient, severing the sternum, cutting and peeling back various layers of tissue in order to give access to the heart and arterial sources, and fitting a sternal retractor frame extending across the incision to maintain the ribs spread apart. The clamps at the proximal ends of the articulating arms of the Medtronic® Octopus 3™ tissue stabilizer and Starfish™ heart positioner can be mounted to the Medtronic® OctoBase™ sternal retractor.
The elongated articulating arms of the Octopus 3™ tissue stabilizer and the Starfish™ heart positioner each comprise a plurality of articulating links strung over an internal cable that extends between the suction member and a proximal knob adjacent the proximal clamp. The proximal knob attached to the cable proximal end can be rotated in a cable tightening direction to stiffen and maintain a shape of the articulating support arm or in the opposite, cable loosening direction to relax the articulating support arm. Each articulating link has opposite ends, one of which is concave and the other of which is convex (e.g., hemispherical). The convex end of one articulating link fits into the concave end of the adjacent articulating link and allows the articulating links to articulate relative to one another if the central cable has not been tensioned to lock the articulating links together. The articulating links are encased within the lumen of a flexible sheath to prevent ingress of body fluids or tissue that might interfere with the articulation of the links.
The distal link is coupled to a suction member that is separately coupled to a flexible tube or vacuum line that is adapted to extend to and be coupled to a vacuum source in the operating room for applying suction to the heart when suction ports of the suction member are applied against the heart. In use, the proximal knob is rotated in the cable loosening direction to release tension on the cable so that a curve or bend can be shaped along the length of the support arm by manipulating the articulating links to dispose the suction member against the epicardium. The proximal knob can then be rotated in the tightening direction to tension the cable, thereby drawing the articulating links together to lock them together in a locked condition that maintains the shape.
The suction member of the Octopus 3™ tissue stabilizer comprises a pair of elongated, malleable, stabilizer pods that are coupled to the distal link to extend in a U-shape, side by side and distally of the distal link. Vacuum lines are coupled to each stabilizer pod, and suction is applied through a plurality of ports of each stabilizer pod. The stabilizer pods are supported by a spreading mechanism extending from the distal link that is indirectly coupled to the tensioning cable. As described in the above-referenced '629 patent, the physician can manually shape the articulating arm to dispose the suction ports of the stabilizer pods against the epicardium, provide suction through the suction lines to grasp the epicardium, and then rotate the proximal knob to tension the cable. The tensioning of the cable concurrently causes the articulating arm to become rigid and the stabilizer pods to spread apart, thereby stabilizing the myocardium between the stabilizer pods while the heart continues to beat.
The Starfish™ heart positioning system employs a three appendage, silicone head mounted to the distal end of a malleable, articulating arm. The silicone head is shaped so that the flexible appendages or legs diverge apart and can engage the heart surface particularly adjacent to the apex of the heart to lift and position the heart when suction is applied. In use, the physician lifts the heart, shapes the articulating arm to apply the three appendages about the apex, provides suction through the suction line to grasp the epicardium, and then rotates the proximal knob in the tensioning direction to tension the cable and make the articulating arm rigid.
Further suction-assisted tissue-engaging devices for use in cardiac surgery through a sternotomy employing articulating arms coupled to distal suction members that are in turn coupled to vacuum lines are disclosed U.S. Pat. No. 6,210,323 and in PCT Publication WO 01/17437 A2.
Surgeons have found that the Octopus 3™ stabilization system and Starfish™ heart positioner provide significant benefits in the above-described operative procedures involving relatively large sternotomies or thoracotomies. However, the vacuum line or lines extending from the suction members coupled to the distal end of the articulating arm can at times be inconvenient and obstruct the view or access in the operative field typically defined by the sternal retractor frame. It would be desirable to be able to enjoy the advantages of such suction-assisted, tissue-manipulation systems employing articulating arms without having vacuum lines extending from the distal suction members.